JPH11324793A - Engine with aluminum piston and aluminum bore resistant to abrasion and scuffing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the long-term resistance to abrasion and scuffing of an aluminum piston driven against a cylinder wall of aluminum and silicon. SOLUTION: The reciprocating engine has an aluminum engine block 24 and an aluminum piston 2. The piston 2 has a skirt part 6 that is made of an aluminum base which is directly coated with a first or hard-anodized layer and a compound polymer coating over the hard-anodized layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an aluminum cylinder bore, abrasion and scuffing.
And a reciprocating engine provided with an aluminum piston resistant to heat.

[0002]

2. Description of the Prior Art It is known to manufacture reciprocating engine blocks from aluminum alloys such as, for example, Al-Si (aluminum and silicon) alloys. Previously, engine blocks composed of eutectic and hypoeutectic aluminum-silicon alloys were made from iron cylinder liners using aluminum-silicon alloy pistons. However, iron liners add weight and cost to the engine and undesirably have a different coefficient of thermal expansion than aluminum blocks and pistons. Instead, one engine manufacturer installs a pre-formed porous liner of aluminum oxide fibers and silicon carbide particles in a mold and penetrates the pre-formed liner to cut the cylinder wall. Engine blocks were fabricated by forcing a hypoeutectic aluminum and silicon alloy casting around it to form. The engine is driven by an iron plate piston to avoid scuffing. Finally, the block is cast from a hypoeutectic alloy of aluminum and silicon (e.g., 390 alloy), and the surface of the cylinder wall is etched with aluminum to expose hard silicon. Engines consisting of these hypoeutectic aluminum bores are available in varnishes containing iron, chromium, nickel, MoS ₂ or graphite, or epoxy resin matrices (patent no.
4,395,442) driven by an aluminum piston coated with oxidized ceramic particles. And, for a piston coated with a smooth film to reduce the sliding friction between the skirt and the cylinder wall, see Rao, US Pat.
No. 3,919, and other patents also issued to Lao, US Pat. No. 5,239,955, Presswood.
No. 4,831,977 to Haldeman, and Patent No. 3,890,950 to Haldeman.
No. 2,817,5 granted to Fleming
See also No. 62 and others. Some of these smooth films contain solid lubricating particles that are carried in a refractory polymer matrix, such as "solid film lubricants" or "composite polymer coatings".
s) ". It is desirable to fabricate the engine block from a eutectic or hypoeutectic aluminum and silicon alloy rather than a hypereutectic alloy. This is because eutectic or hypoeutectic alloys are cheaper and have good casting and machining performance. Furthermore, to reduce the weight and cost, and, in order to improve the heat conversion performance, coarse making products from a previous eutectic or hypo-iron liner and Al ₂ O ₃ was used in conjunction with alloy block crystalliser -SiC Is desirable. However, driving the aluminum piston against the aluminum cylinder wall results in significant wear of the cylinder wall and the skirt of the piston (i.e., between two parts sliding together with the lubrication oil running out). Viscous wear). Such excellent resistance to scuffing is obtained between eutectic and hypoeutectic blocks and aluminum pistons whose piston skirt is coated with a solid film lubricant. However, the wear resistance and durability of such coatings in this application are unsuitable for long life engines.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to an alloy of aluminum and silicon having a hypoeutectic, eutectic, or hypereutectic cylinder wall by increasing the wear resistance of a composite polymer coating applied to a piston. It is an object of the present invention to provide a long-term scuffing resistance between an aluminum piston driven against an aluminum and silicon cylinder wall regardless of which one is used.

[0004]

According to the present invention, there is provided a reciprocating engine having a block comprising an alloy of aluminum and silicon, the block defining a cylinder bore and having at least the same composition as the block base. It has one internal cylinder. Therefore,
If the block is cast from a hypoeutectic alloy of aluminum and silicon, the cylinder walls will have the same composition. The cylinder wall is machined to provide a surface finish having _a surface roughness Ra on average of about 0.09 to about 0.25 microns. This engine
An aluminum and silicon alloy piston with a skirt having an outer surface facing the cylinder wall is also provided. The surface of the skirt has a hard anodized coating applied to the surface and a composite polymer coating formed over the hard anodized coating. The composite polymer coating includes a heat resistant polymer that can withstand the operating temperature of the engine, and further includes a plurality of solid lubricating particles therein. The hard anodized coating underneath the composite polymer coating helps to achieve much lower and more consistent wear of the aluminum cylinder walls, and a much lower wear rate of the composite polymer coating on the piston, This extends the useful life of the engine. The hard anodized underlayer was 30 times less than the piston having only the composite polymer coating without the anodized underlayer.
Tests have shown that the wear rate of the composite polymer coating is reduced by as much as%. Significant reductions in cylinder wall wear rates have also been observed. According to a preferred embodiment of the present invention, the hard anodized coating has a thickness of about 15 to about 25 microns, most preferably 20 microns. And the composite polymer coating is preferably made of graphite and carbon monofluid.
oride), boron nitride, and solid lubricating particles selected from the group comprising sulfides, including molybdenum, tungsten and titanium, selenides and tellurides. These solid lubricating particles are made of high temperature epoxy (he
at temperature epoxy), thermosetting polyimides (heat
curable polyimides), polyamide imide (polyamide)
imide), polyphenylene sulfide, and polyaryl sulfone, held in a polymer matrix selected from the group comprising:

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
The following for certain embodiments of the invention given
When considered in light of the detailed description that follows.
Will be better understood. FIG. 1 shows a top 4 and the top 4
Aluminum having a skirt portion 6 hanging therefrom
Piston 2 and internal strength not numbered
To attach piston structure to piston 2
The bore for accommodating the piston pin. Pair of
Upper ring grooves 8 and 10 receive compression rings 12 and 14.
And the lower ring groove 16 is
Luling 18 is accepted. Piston 2 is the engine
Defined by an annular cylinder wall 22 in block 24
Reciprocate in the cylinder bore 20 to be moved. engine
Block 24 is cast from an alloy of aluminum and silicon
And it can also be made from hypereutectic alloys
Preferably, eutectic or hypoeutectic aluminum and silicon
Preferably, it is cast from Recon's alloy. According to the present invention
For example, as shown in FIG.
The part 6 has an outer surface 26 on which the dark
A hard anode so that the aluminum oxide layer 28 is formed.
The treatment has been applied. Hard anodized coating
Electrochemically on the surface of aluminum where it came
Formed and at least 540 micro Knoop hardness
With an aluminum oxide layer having (at 5 grams weight)
is there. The oxide layer according to the present invention has a thickness of about 540 to about 600.
Between about 560 micro Knoop hardnesses (ie, 5
Gram weight). Aluminum anodizing is a well-known process.
Roses. This process allows the aluminum substrate
Form an anode in the electrolyte, and
Reacts with oxygen provided by vaporization, and on this anode surface
The process of electrochemical conversion to aluminum oxide
Pass. Many different acidic substances are used,
Muric, sulfuric, and oxalic acids are the most common electrolytes.
In particular, sulfuric acid is most often used. Sulfuric acid is low cost
In addition to rapid processing, high conductivity of sulfuric acid and film
Relatively low due to its ability to penetrate to the underlying metal
This is because the operation voltage can be used. Anode coating
Characteristics include the electrolyte used, the concentration and temperature of the electrolyte,
It depends on the current used and the processing time. For hard coating
In contrast, the ambient temperature (for example, approximately −2 ° C. to 5
° C) and a suitably concentrated sulfuric acid electrolyte (eg,
About 10% to 20% by weight). In particular, by weight
12% to 15% H_TwoSO_FourIs preferred. Preferred process
To form an appropriate hard coating according to the
The piston is grease, corrosive,
Chemical to remove all (naturally occurring) oxides
To be cleaned. One good cleaning technique is room temperature stones.
Scrub the piston with a soap solution, then cold water
Too, and alkaline cleaning not generally available
Immerse in the solution at about 60 ° C. for about 3 minutes. Or that
Then, the cleaning operation is completed by cooling and rinsing. Achieve the same result
Other cleaning controls are also effective. Next, the cleaned piste
Is 12% H_TwoSO_FourImmersed in 0 ° C electrolyte containing
And how thick coatings are needed
About 3 A / dm for about 8 to about 20 minutes depending on^Two
Anodized at a current density of One coating thickness
Generally in the range of about 8 microns to about 20 microns;
About 20 microns is preferred. The temperature, concentration and
Acid with a thickness of about 20 microns under conditions of current and current density
It takes about 10 minutes to produce the chloride. Before anodizing
In addition, the piston controls where the oxide is formed,
Appropriately to exclude places where chloride should not be formed
Masked. In this regard, typically at least
The top is covered with a mask member, so that only the skirt is
Anodized. On the other hand, between the ring 12 and the groove 8, a high
Increases resistance to warm scuffing or micro-welding
To anodize the inside of the top compression ring groove 8
It has been known. So what masks are made
The compression ring groove 8 at the top is left exposed, and
As a result, when the skirt portion 6 is covered with the oxide layer 30,
At the same time, it is formed in the groove. Following the anodization,
If the stone is exposed to a dirty environment, this piston will
Before the compound polymer coating 32 is applied, the soap and
After being cleaned with water, it is dried. After cleaning, the composite polymer
-The coating is applied over the anodized layer
You. Preferably, such a coating is about 12 micron
Ron to about 8 microns thick, smooth solid particles
(For example, graphite, carbon monofluoride, and boron nitride
Including molybdenum, tungsten and titanium
Sulfide, selenide and telluride). these
Solid particles include, for example, high temperature epoxy, thermosetting polyimide
, Polyamide imide, polyphenylene sulfide,
Heat resistance (ie, engine operation)
Sufficient resistance to maintain performance at operating temperature) Included in polymer
It is. One such coating useful in the present invention
Is from about 5% to about 30% by volume in the polyamideimide.
% Graphite. Other suitable composite polymer coats
About 2% by volume in polyamideimide
From about 20% graphite particles to about 2% by volume
About 20% MoS _Twoincluding. Composite polymer coating
Solutions for coating the coating are commercially available. Like that
One of the coating solutions is 31% by weight.
% Polyamideimide, 17% graphite, 51%
N-methyl group pyrrolidone (N-metylpyrolidone)
Mi, Dow Corning Corporation Association
Available from the company. Another such solution is 10
Mg / m^ThreeMoS2, 25Mg / m^ThreeOf graphite,
434 Mg / m^ThreeXylene, 90 Mg / m^ThreeDioxa
And 35 Mg / m^ThreeContaining dimethylacetylene
Available from Wamura Research Institute. Smooth particles
Has a length of about 3 to about 15 microns and a diameter of about 1 to 5
Equiaxed or fine in the form of fibers in the micron range
It can take any of the elongated shapes. The composite port of the present invention
Rimmer coatings are known to those skilled in the art,
Silk screen, pad printing
Various methods, including techniques such as pad printing.
Can be used. While applying such a method
First, the polymer is dissolved in a suitable solvent.
Following the coating process, the coated piston is
It is dried to remove the solution. Polyamide imide is
When used as a rimer matrix, the polymer
The piston is allowed to set for about 15-60 minutes to cure.
Bake at 180 ° C to about 200 ° C. Other binders are hard
Therefore, different times and temperatures are required as needed. The weight of the present invention
The key aspect is the smoothness of the cylinder wall surface. this
In terms of points, the cylinder wall surface depends on the cylinder wall
Averaged to reduce wear of composite polymer coatings
Surface roughness R_aUntil about 0.09 to about 0.25
Polished. In contrast, cast iron cylinder walls are
Typically, the average surface roughness R _aIs about 0.32 to about
Hypereutectic polished and etched to 0.80
Cylinder wall made of aluminum and silicon alloy
Is a surface roughness R of about 0.20 to 0.30_ahave. Machine
Is a hypereutectic alloy that has been machined but not etched
Can be used successfully in the present invention
You. Bore surface has roughness less than 0.25 micron
When this is done, the bore surface
It becomes smoother gradually by continuous driving. Only
On the contrary, the surface roughness of the bore is 0.25 microns.
When larger, this bore surface is
With the continuous driving of the
The wear rate of the composite polymer coating is greatly increased. Bo
When the surface is smaller than 0.09 microns, the oil
The ability is no longer good, and appropriate smoothness is achieved.
Can only provide insufficient oil. Accelerated benchite
Strike (ie, Cameron Print Reciprocating Machine)
(Cameron Plint Reciprocating Machine)
T) and engine power measurement tests to ensure wear and scuff
It was performed to evaluate the resistance of the wing. These te
The strike is (1) coated with a composite polymer coating only.
Piston (2) Hard anodized piston surface
Coated with a composite polymer coating on the
Each was performed against Ston. This piston is weight
With 7% to 18% silicon content by weight
The cylinder was driven against the bore surface. Ki
In the Cameron Print Bench Test, the piston
While part of the cart is reciprocating, the cylinder
A) It was rubbed against a part of the surface. This test
When performed with lubricating oil, it is a wear test.
You. When this test is performed without lubricant, it is
It becomes a scuffing test. In the wear test, the maximum
Load that applies 10 Mpa contact stress at dual frequency hertz
Was applied at 125 ° C. Lubricating oil is "SAE5W30"
Met. The stroke is at a reciprocating frequency of 10 Hz.
6.77 mm. The test period was 20 hours
Was. Next, the depth of wear of the tested sample is measured.
Was. Scuffing test with piston skirt
Part of the part has a maximum reciprocating frequency of 4 to 10 Mpa
Various loads that apply a range of contact stresses are applied
Is rubbed against a part of the cylinder bore surface
Was. The temperature during this test was 85 ° C, and the test period was
15 minutes. Friction and contact between two samples
Changes in air resistance were constantly monitored. Increased friction and
Decrease in electrical contact resistance is due to scuffing during test
It was shown to have occurred. The load leading to the start of scuffing
Weight and time are used to rank scuffing resistance
Used for These tests are based on composite polymer coatings.
Only (ie, no anodized primer coating
Or composite poly on hard anodized coating
Hypoeutectic, hypereutectic or eutectic alloy
When driven against the bore, iron or nickel
Superior piston over piston plated with alloy
It has cuffing resistance. These tests
A composite polymer core over a hard anodized coating
Coating is a composite port coated directly on aluminum.
Much lower than Rimmer Coating (about 1/5 to about
1/3) and also produced constant wear. This
20 hours after the wear bench test,
The thickness of the polymer coating is measured and at the start
Was compared with the thickness in These tests are
A piston with an under-treated pole coating
On average about 30% lower than piston without oxide underlayer
The wear rate was high. Finally anodized
With a composite polymer coating on the bottom layer
Aluminum and both hypoeutectic and hypereutectic
Assembled from silicon alloy cylinder wall surface
The engine is a low-temperature scuff by Reynolds Metal Company
Testing by General Motors Corporation
Passed both hot scuffing tests. Anodizing co
To increase wear resistance attributed to
Although the cause is not well understood, (a) hard anodic treatment
Is a softer polymer than uncoated aluminum
-A solid solid substrate that better supports the coating
Factor, or (b) hard anodizing
Better adhesion of composite polymer coating to stones
Promote composite polymer coating accept slightly
Cause of providing a rough surface to the surface?
Are considered to be The present invention relates to certain features of the present invention.
Although disclosed in terms of certain embodiments, the present invention does not
Is not limited to
Defined only by range.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a piston and blocks around the piston.

FIG. 2 is an enlarged view of a piston surface in a region indicated by reference numeral 2 in FIG. 1;

[Explanation of symbols]

 2 Piston 6 Skirt 20 Cylinder bore 22 Internal cylinder wall 28 Hard anodized coating 32 Composite polymer coating

Continuation of the front page (72) Inventor Peter Vernia 48306, Michigan, USA, Rochester Hills, Torah Hase Drive 2763 (72) Inventor Simon Chin-Yu Tun 48306, Michigan, USA, Rochester Hills, Haverhill Hill Drive 1871

Claims (3)

[Claims] 1. A first aluminum alloy block (2)
4) and the first aluminum alloy block (2)
4) at least one internal cylinder wall (22) formed to define a cylinder bore (20) within
And a second aluminum alloy piston (2) reciprocating in the bore (20), wherein the wall (22) averages between about 0.09 to about 0.5 mm. The piston (2) has a skirt (6) having an outer surface (26) facing the wall, having _a surface roughness Ra of 25 microns, the surface being attached to a first surface attached to the surface. 1 hard anodized coating (28);
A second composite polymer coating (32) on the hard anodized coating (28), the second composite polymer coating comprising a plurality of solid lubricants in a refractory polymer matrix that can withstand the operating temperature of the engine. The said reciprocating engine containing a particle. 2. The hard anodized coating (28).
The engine of any of the preceding claims, wherein the has a thickness of about 8 microns to about 25 microns and the composite polymer coating (32) has a thickness of about 12 microns to about 18 microns. 3. The solid lubricating particles include graphite,
Selected from the group consisting of carbon monofluoride, boron nitride, and sulfides including molybdenum, tungsten and titanium, selenides and tellurides, wherein the polymer matrix is a high temperature epoxy, thermoset polyimides,
The engine according to claim 1, wherein the engine is selected from the group comprising polyamide imide, polyphenylene sulfide and polyaryl sulfone.